A Universal Serial Bus (USB) is a port and communication protocol available in computers and various electronic devices based on the same interfacing method, such that the USB allows data to be easily transferred between computers and electronic devices designed to use the USB over the same type of port, generally called a USB port.
USB allows coupling of peripheral devices to a computer system, and is a serial cable bus that supports data exchange between a host computer and a wide range of simultaneously accessible devices.
The bus allows peripherals to be attached, configured, used, and detached while the host computer is in operation. For example, USB printers, scanners, digital cameras, storage devices, card readers etc. may communicate with a host system over USB.
A communication method for USB is a master-slave asymmetrical communication method. In this case, although a master device acting as a host device may have high implementation complexity, a slave device may be simplified in structure. In addition, a plurality of slave devices may be connected to a single host device according to the USB communication method, and, as such, the above-mentioned USB communication method has been widely used in personal computers (PCs) and other computer systems throughout the world.
An asymmetrical multiplex communication method for USB has been designed to allow only one host to communicate with a slave, such that it is difficult for two or more hosts to be multiplexed with a plurality of slaves according to the asymmetrical multiplexing communication method for USB.
In addition, since the present USB standard specification is unable to support such communication, plural USB ports need to be physically installed for connection of plural hosts.